/*
// Licensed to Julian Hyde under one or more contributor license
// agreements. See the NOTICE file distributed with this work for
// additional information regarding copyright ownership.
//
// Julian Hyde licenses this file to you under the Apache License,
// Version 2.0 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 */
package org.olap4j.query;

/**
 * Describes what methods a Query Node must implement in order to support listeners. Olap4j's query model provides an
 * abstract implementation of interface.
 * 
 * @author Luc Boudreau
 */
interface QueryNode {

	/**
	 * Registers a new listener for a QueryNode.
	 * 
	 * @param l
	 *            The new listener object, implementation of QueryNodeListener
	 * @see org.olap4j.query.QueryNodeListener
	 */
	public void addQueryNodeListener(QueryNodeListener l);

	/**
	 * De-registers a new listener for a QueryNode. If the listener object passed as a parameter was not registered, the
	 * method will return silently.
	 * 
	 * @param l
	 *            The listener object to de-register.
	 * @see org.olap4j.query.QueryNodeListener
	 */
	public void removeQueryNodeListener(QueryNodeListener l);
}
// End QueryNode.java
